Suppress leak of ProcessSingleton::LinuxWatcher on shutdown.

tools/valgrind/memcheck/suppressions.txt

Index: tools/valgrind/memcheck/suppressions.txt
diff --git a/tools/valgrind/memcheck/suppressions.txt b/tools/valgrind/memcheck/suppressions.txt
index 6f36a4f377e71c9599f13738c3545700dd6e776f..1a2d557407eed2bed391b8c6a7f9e18e6a77c509 100644
--- a/tools/valgrind/memcheck/suppressions.txt
+++ b/tools/valgrind/memcheck/suppressions.txt
@@ -5213,6 +5213,16 @@
    fun:_ZN7WebCore14SVGTextMetrics21measureCharacterRangeEPNS_19RenderSVGInlineTextEjj
    fun:_ZNK7WebCore30SVGTextLayoutAttributesBuilder25propagateLayoutAttributesEPNS_12RenderObjectERN3WTF6VectorINS_23SVGTextLayoutAttributesELm0EEERjRt
 }
+{
+   # ProcessSingleton::LinuxWatcher is marked DeleteOnIOThread.  Sometimes it
+   # leaks on shutdown instead of getting deleted.  The destructor doesn't do
+   # anything important, so this shouldn't be a big deal.
+   bug_104578
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN16ProcessSingletonC1ERK8FilePath
+   fun:_ZN22ChromeBrowserMainParts25PreMainMessageLoopRunImplEv
+}
 
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